Do you let them free range? What kind of snakes? Maybe a run with tight fencing - like 1/4" hardware cloth sides, top and bottom and around all gates or openings would keep them out. Years ago someone said they used poultry wire on the ground and rolled it out like a slinky toy. The snakes would try to get throw the small openings and get caught up and die there. They said then other scavengers would eat them off the wire.